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' Resa es s. 22,1924.

' {Y I UN ED ject of the King or.

,sTA'rss jR'e. 15,750 PATENT OFFICE.

;mmax or Lennon, anemia.

is a..1.',."t.i. ..m. assaaao, ama Iovemb er 1, 1021, Serial Io. scam, 'aua January as, use.

. Application for rciaauefled September sums. Serial Il o. man.-

To allwhom'it may cm'wem: p 'Be it known that I Hmmr Hams, a sub- Great Britain, residing inLondon, En land, have inventedcertain Ii new and usefu Improvements in' Refining Lead,'of which the following is a specifics- Y caustic alkali, either with or without an adgen. (or-a source of oxy' en) tion.

Several rea nts have been suggested for dezincing lea among them caustic. soda;

this re'a ent, however, is. not particularl activean parts with sodium to the lea A mixture of zinc chlorid and litharge is .effective, butthe litharge must be free from silver and therefore expensive, and a con;

ll siderable amount of the zinc chlorid volatilizes and is lost at the temperature ofthe= molten lead. It has also been proposed to utilize a double salt of zinc chlorid with the litharge or with lead sulphide ore in a proce'sswhere the quantity of litharge or lead sulphide ore used must be such that the amount of lead contained therein is at least chemically e uivalent to the zinc in the metal to be purifie h; that is to say the lead conaa' tained' in the litharge or sulphide ore must be in'the ratio of about 207 parts of leadto each 65 .parts of zinc contained in'the lead to I be purified. (See German Patent 241,483.) This last process is also objectionable because of the expense of producin the necessary amount of hthar or sulphi e ore free from silver and other impurities.

v I have found that a fused alkali chlorid will react with molten lead containing zinc to remove the latter from the lead. The

temperature required, however, is so high that loss of lead occurs and alkali metal passes into the'lead from which itcannot easily be eliminated. i

Oneof the objects of my invention is to avoid these objections by using in conjunction with .the alkali chlorid a substance or' substances which reduce its melting point. Preferably the melting point of the reagent thus formed should not exceed 500 C. A further object is to provide an efficient and inexpensive process utilizing such a mixture.

I avealso found that at temperatures not exceedin zinc can oxidized .by atmosphericoxygen to such an extent as to render unnecessary the addition of other oxygen (or-a source of oxygen) for the dezincing.

500 (1., molten lead containing With these objects in view my invention in one aspect comprises as the reagent the use of a mixture of alkali chlorid with another com und or compounds of an alkali metal, which will reduce the melting oint of the alkali chlorid, such for examp e, as

dition of 0 other than t at derived from atmosp eric oxidization ing of the dezincing at the reduced temperature, preferably below that where any apand also comprises the conductpreciable amount of alkali metal passes per- I inanently into the lead. I

.A mixture of caustic alkali and alkali chlorid is particularly useful since-the mixture does not part with sodium to the lead.

at the temperature at which it can be used, T

and the reaction which removes the zinc is 7 not dependent on oxygen other than that contained in the mixture due, I believe, to the capacity of the mixture to absorb oxygen mixed; although oxygen added in the form of relatively small quantities of litharge or forced air may hasten the process.

In another aspect my invention comprises, with the maintaining of the relatively low temperature, the use of zinc chlorid and alkali chlorid as the reagent, with or without an addition of oxygen (or a source of oxygen) other than that derived from atmospheric oxidization but in the case of an added source of oxygen this phase of my invention does not contemplate or include a process where the oxygen source is lead oxide or an ore of lead oxide, used in such quantity that the contained lead is in amount chemically equivalent to the zinc in the metal to be purified; that is to say where a process is carried out depending upon .this relatively large amount of lead oxide in conjunction.

does, however, not exclude the use of rela- 'tively small amounts of lead oxide such as when said mixture and molten lead are I one may have on hand or may desire to redues to metallic leadancl which may be regardcd as incidental to but not necessary or the carrying out of my dezincing process. As in the case of the caustic alkali in the .first aspect of the invention, zinc chlorid in a will thereafter be 'The reagent is not this case also lowers the melting point of the alkali chlorid, although it is not as eifective or desirable as the caustic alkali; but its efiectiveness may be improved when the addition of oxygen (ora source of oxygen) is not ob'ectionable.

In t than the known reagent consisting of zinc chlorid and lithar alone and less costly in zinc chlorid since t e latter does not volatilize so readily when used in conjunction with alkali chlond. This phase of my invention is also more efl'ective than the known proc ess utilizin a mixture of litharge, zinc chlorid and so ium chlorid and requirin litharg in such quantities as to contain ead in an amount at least chemically equivalent to the zinc in the metal to be purified.

I will further describe my invention by giving certain examples of the manner inwhich it may be practiced, and the invention more particularly pointed out in the appended claims.

The followmg examples illustrate the in vention $11) A mixture of 24 lbs. of sodium chlorid an 25.5"lbs. of caustic soda is brought into intimate contact (such as by the met od described in my application for U. S. atent Serial No. 354,852) with 4 tons of lea containincg 0.65 per cent of zinc, heated to about 500 The zinc is chloridized and oxidized and is found as a scum or dros'smixed with the re t.

(2) e lead to be dezinced; is brought into intimate contact at a temperature about 500 (1., with the double chlorid of zinc and sodium amountin the zinc container? in the lead. I Air is either blown throu h the lead during the operation or supp led in the manner described in my-said application for U. S. atent Serial No. 354,852. The oxidized and chloridized zinc is removed as referred to in examplel. exhausted by a single treatment and may be used again.

It is well known in the art that lead may contain other metallic impurities than zinc, such for exam l'e as tin, arsenic and antimony; and while I have described my procass in detail as applied to the refining of molten lead b the removal of zinc; in such of the appen ed claims as I use the term refining I do not wish to be understood as being limited to the removal of zinc, but aim by such claims to cover the treatment of molten lead by the process therein claimed, for the removal of any metallic impuritiesv that may be removed by such treatment; as will be understood by those skilled in the art.

In this application I aim to cover that phase or specie of my invention wherein the alkali chlorid is used in conjunction with another compound or-compounds of an alkali metal which will lower the melting tion as is case the mixture is more efl'ective' perature below that wh to 3.6 times the weight of sodium chlorid and point of the alkali chlorid, such, for exam ple, as caustic alkali; whereas in my coending re-i'ssue aplplication Sr. No. 665,236 aim to cover features of the invenare not herein claimed, including among others that specie of my invention wherem the alkali c lorid is used in conjunction with zinc chlorid;

Having thus described the'nature of the said invention and the best means I know of carrying the same into practical efiect, I claim 1. Process of dezincing lead which comprises bringing the molten lead into intimate contact with a mixture comprising caustic alkali and alkali chlorid at a'temere any appreciable amount of alkali metal passes permanently into the lead, and maintaining the mixture below said temperature.

2. Process of dezincing lead which comprises bringing the molten lead into intimate contact with a fluid mixture comprising caustic soda and sodium chlorid at a temperature below that where any appreciable amount of alkali metal passes permanently into the lead, and maintaining the mixture below said temperature, 3. Process of dezincing lead which comprises bringin the molten lead into intimate contact with a molten-mixture comprising caustic alkali and alkali chlorid at a tem erature not exceeding about 500 (3., con ucting the operation underv oxidizing conditions, and maintaining the mixture not exceeding saidv temperature.

4. Process of dezincing lead which comprises bringing the molten lead into intimate contact with a molten mixture comprising caustic alkali and alkali chlorid at a temperature not exceeding about 500 0., maintaining the mixture not exceeding said temperature and conducting the operation in such manner as to effect atmospheric oxidization for the dezincing reaction so as to be able to dispense Wholly or partially with the addition of other oxygen (or a source of ox gen).

5. P rocess of dezincinglead which comprises bringing the molten lead into intimate contact with a mixture comprising alkali chlorid and another compound or compounds of an alkali metal, which will lower the melting point of the alkali chlorid so as not to exceed about 500 C., and main- 1 taining the mixture not to exceed said tem- I perature.

' 6. A process of dezincing lead which consists in bringing the molten lead into intimate contact with a molten mixture of alkali chlorid and caustic alkali.

Process of dezincing lead which comprises bringing the molten lead into intimate contact with a,v molten mixture comprisi at least suflicient caustic 180 III alkali to reduce the melting point of the mixture substantially below that of the sodium chlorid, maintaining the mixture substantiall below the melting point of sodium chlorid and conducting the operation under oxidizin conditions.

8. Process 0? dezincing lead which comprises bringing the molten lead, under atmospheric oxidizing conditions, into intimate contact with a molten mixture comprising caustic alkali and alkali chlorid at a temperature below that where any appreciable amount of alkali metal passes perma nently into the lead, and maintaining the mixture below said temperature. I

9. Process of refinin lead which comprises bringing the mo ten lead into intimate contact with a molten mixture comprising sodium chlorid and at least suflicient caustic alkali to reduce the melting point of the mixture substantially below that of sodium chlorid and maintaining the mixture substantially below the melting point of sodium chlorid.

10. Process of refining lead which comprises bringing the molten lead into intimate contact with a molten mixture com- 11. Process of refining lead which comprises bringing the molten lead into intimate contact with a molten mixture comprising caustic alkali and alkali chlorid at a temperature below that where any appreciable amount of alkali metal passes permanently into the lead, conducting the operation under oxidizing conditions, and maintaining the mixture below said temperature.

12. Process of refining lead which comprises bringin the molten lead, under atmospheric oxi izin'g conditions, into intimate contact with a molten mixture coinprising sodium chlorid and at least suflicient caustic alkali to reduce the melting point of the mixture substantially below that of sodium chlorid, and maintainin the mixture substantially below the me ting point of sodium chlorid.

In testimony whereof I have signed my name to this specification.

HENRY HARRIS. 

